The two-stroke gasoline engine is a well known power source for outboard motors, snow mobiles, motor boats, motorcycles, scooters, mopeds, gensets and a variety of landscaping equipment, e.g., lawn mowers, chain saws, string trimmers and blowers. The widespread use of two stroke gasoline engines is primarily due to their simple design and lightweight construction, their ability to provide high power output with quick starts at low temperature and their relatively low cost. Two-stroke gasoline engines are operated using a mixture of gasoline and a lubricant in prescribed proportions. Because the fuel contains a gasoline lubricant mixture, large amounts of smoke are generated and emitted in the exhaust. The lubricant must provide satisfactory performance characteristics under severe operating conditions. Lubricants for two-stroke gasoline engines are traditionally composed of a mineral oil or synthetic base fluid, performance additive(s) and a solvent, ordinarily a relatively low boiling petroleum distillate, to enhance gasoline/lubricant miscibility.
The technologies developed to date for reducing exhaust emissions from four-stroke car and truck gasoline engines have not been successfully adapted to two-stroke gasoline engines. Hence, there is growing public concern over the high levels of hydrocarbon emissions from these small gasoline engines, as these hydrocarbons do not readily biodegrade. The mineral hydrocarbon emissions are a consequence of the basic design of the gasoline engine. Specifically, in the power stroke of a typical two-stroke gasoline engine, air, oil and fuel are drawn into the crankcase as the combined charge is compressed in the space above the piston. In the exhaust stroke, the burnt gases are discharged through exhaust ports, and a fresh combustible charge is transferred from the crankcase to the space above the piston. Because the exhaust ports open before and close after transfer of the fresh combustible charge occurs, as much as 18% of the fresh charge will be discharged unburned with the exhaust. Consequently, hydrocarbon emissions far exceed the level of emissions from a comparable four-cycle engine.
Water-cooled outboard motors exhaust directly into the water, giving rise to water pollution, whereas the other devices mentioned above, which are equipped with air-cooled two-stroke gasoline engines, produce emissions that pose a serious air pollution problem. For example, many two-stroke gasoline engines produce up to fifty times the pollution of truck engines per horsepower hour. Visible smoke emissions in the exhaust from two-stroke gasoline engines have also recently come under increased scrutiny and regulation. In addition, smoky emissions from two-cycle gasoline engines are also becoming a problem from an aesthetic standpoint.
The petroleum based lubricating oils are hydrocarbons consisting of naphthenes, paraffins, aromatics, polynuclear aromatics and unsaturates. Various additives, which are primarily chemicals of defined composition or structure, are added to the lube oils to improve the physico-chemical properties and performance.
Petroleum based lube oils, generally suffer from many disadvantages such as high toxicity to the environment, poor biodegradability and inconsistent characteristics with change in crude oil composition. The other types of lubricants known as synthetic lubricants are deigned for use in extreme conditions of temperature, pressure, radiation or chemical and have excellent lubricity and thermal stability. The synthetic lubricants are relatively costly, also toxic to environment and are may not be eco-friendly. Commonly used synthetic lubricants for various applications are,
a) Poly-glycols,
b) polybutenes,
c) dibasic acid esters,
d) fluoropolymers,
e) polyol esters,
f) phosphate esters,
g) silicones,
h) poly-alpha olefins,
i) other similar fluids.
The above-noted pollution and smoke problems are exacerbated by the presence of volatile organic solvents in the lubricant. Moreover, some of the solvents used as miscibility enhancers have relatively low flash points, thus creating a potential fire risk, which is of particular concern in connection with the storage and transportation of such products.
In the prior art for producing two-stroke gasoline engine lube oils, generally, mineral oils or mineral oil with synthetic fluids or complex ester of fatty acids were used to enhance the performance. Smoke and eco-friendliness were not the main criteria.
Certain types of monoesters from non-edible vegetable oils are useful to generate reduced amounts of observable smoke as a result of combustion in a two-cycle gasoline engine, can be used on lower concentration and compatible to alkyl benzene.
Reference may be made to U.S. Pat. No. 6,197,731, Zehler, et al., Mar. 6, 2001, Henkel Corporation (Gulph Mills, Pa.) Smokeless two-cycle engine lubricants Ester base stocks for two-cycle gasoline engine lubricant compositions are disclosed which produce lower amounts of observable smoke in the exhaust emitted as a result of combustion in a two-cycle gasoline engine, require no miscibility-enhancing solvents, have a viscosity of 3.0 cst to 20.0 cst at 100.degree. C. and a smoke index of at least 75. Some of the esters are biodegradable. (Here, synthetic esters of polyol type were used).
Reference may be made to U.S. Pat. No. 5,498,353, Lin, et al., Mar. 12, 1996, Chinese Petroleum Corp. (TW) Semi-synthetic two-stroke engine oil formulation. A semi-synthetic two-stroke engine oil formulation which comprises a base oil consisting of a high-viscosity mineral oil, a medium-viscosity mineral oil, a solvent and a mixture of three polyisobutylenes with different molecular weights, and appropriate detergents and dispersants. This semi-synthetic two-stroke engine has both high lubricity and high detergency, and also meets the requirements of low smoke and low exhaust system blocking. (Here, blend of mineral oil and synthetic oil are used)
Reference may be made to U.S. Pat. No. 5,475,171, McMahon, et al., Dec. 12, 1995 BP Chemicals Limited (London, GB2) Two-stroke engine oils. This invention relates to a two-stroke engine oil which comprises polybutene base oils which are either very low in or are substantially free of n-butenes in the polymer backbone. The absence of n-butenes in the polybutenes significantly reduces smoke emission in exhaust gases generated by the use of the engine oil. Polybutenes such as ULTRAVIS® which are substantially free of chlorine and have a high degree of terminal unsaturation are particularly preferred. (Here, blend of mineral oil and synthetic oil are used)
Reference may be made to U.S. Pat. No. 5,378,249, Morrison, Jan. 3, 1995 Pennzoil Products Company (Houston, Tex.) Biodegradable lubricant. A biodegradable two-cycle engine oil composition comprises about (a) 20 to 85 wt. % of a heavy ester or a mixture of heavy ester oils characterized by a kinematic viscosity of at least about 7.0 cst at 100.degree. C., (b) 10 to 85 wt. % of a light ester oil or a mixture of light ester oils characterized by a kinematic viscosity of less than about 6.0 cst at 100.degree. C., and optionally an additive, wherein the composition has a biodegradability of at least about 66% as measured by the CEC L-33-T-82 method. (Here, blend of mineral oil and synthetic oil are used)
Reference may be made to U.S. Pat. No. 6,281,173, Tanaka, et al. Aug. 28, 2001 Castrol Limited (Wiltshire, GB), ‘Two-stroke motorcycle lubricant’ describes a two-stroke motorcycle lubricant comprising a base oil having a viscosity at 100.degree. C. of less than 8 cst and a pour point below −30.degree. C., preferably below −39.degree. C. The two-stroke motorcycle lubricant further comprises a detergent system based on an ashless, oil-soluble amine. The two-stroke motorcycle lubricant exhibits high levels of cleanliness and low levels of exhaust smoke, whilst maintaining high load carrying capacity. The two-stroke motorcycle lubricant may be dyed. (here mineral oil base stocks were used)
Reference may be made to U.S. Pat. No. 6,573,224, McNeil, et al., Jun. 3, 2003, Bardahl Manufacturing Corporation (Seattle, Wash.) Two-cycle engine lubricant composition comprising an ester copolymer and a diester. Improved performance of two-cycle and four-cycle engines is achieved by adding to the oil or fuel of such engines a composition that contains a copolymer of an alpha-olefin and a dialkyl fumarate or maleate and/or a synthetic diester compound that has about 30 carbon atoms. For two-cycle engines, the composition preferably contains both chemicals, in addition to an octane booster such as methylcyclopentadienyl manganese tricarbonyl. For four-cycle engines, the composition contains at least one of the copolymer and diester, in addition to a molybdenum or bismuth salt, dimercapto 1,3,4-thiadiazole and sulfur-phosphorous EP and/or chlorinated paraffin. The composition can also act to improve gear and grease lubrication and provide improved lubricity to fuels. (Here, synthetic oil are used)
In view of the growing concern about the environment and conservation of petroleum there is a need for eco-friendly lubricating oil for two-stroke gasoline engine, which are derived from alternate sources without a diluent and reduce smoke, perform better or at least at par with the mineral lube oil and be cost effective.
A patent filled by the inventors of the present invention disclosed the use of Heavy Alkyl Benzene alkaline earth metal sulfonates used as detergent-dispersant-anti rust additive in various types of lubricants (Patent application IPA number 1306/DEL/1998 & 1307/DEL/1998 by A. K. Singh et al assigned to CSIR). The alkyl benzenes are mono, di and poly substituted alkyl aromatics having one benzene or toluene aromatic ring and straight or branched paraffinic chains, preferably mono and di alkyl benzene. Alkyl benzenes are produced, as by-products during the preparation of, (1) linear alkyl benzene (LAB) in detergent industry, (2) heavy aromatic produced in catalytic reformer, and (3) naphtha or gas steam cracker liquid product. Alkyl benzene consists of substituted benzenes and no poly-aromatics/condensed ring or olefinic compounds are present in the alkyl benzenes. It can be used as an alternate to mineral base stock of lubricants. It will reduce the hazard potential of the lubricants. It will provide required properties such as good lubricating oil for two stroke gasoline engine properties, lubricity, load carrying, stability, anti-corrosion properties and more eco-friendliness.